The existence of nicotinic acetylcholine receptors (nAChR) on lymphocytes remains controversial. We attempted to show the existence of nAChR on murine lymphocytes. The intraperitoneal injection of nicotine induced the lymphocytosis in the spleen on day 3. Although freshly isolated lymphocytes bound small quantities of fluorescein isothiocyanate (FITC)- conjugated α-bungarotoxin (αBuTx), they began to bind αBuTx after incubation in medium. In contrast to granulocytes, various lymphocyte subsets obtained from various lymphoid organs were found to bind αBuTx. Affinity purification of αBuTx-binding protein revealed that lymphocytes expressed the same nAChR molecules as those of muscle. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that lymphocytes expressed the α-subunit mRNA of nAChR. These results suggest that lymphocytes carry nAChR on the surface and are stimulated directly via their nAChR by parasympathetic nerve stimuli.